Increasing attention is being focused on the importance of good indoor air quality and its affect on health. The U.S. Environmental Protection Agency (EPA) has named indoor air pollution as one of the most urgent national problems. While many factors can contribute to poor indoor air quality, much attention has recently been given to the detrimental affects of fungi such as molds and yeasts. For example, a Mayo Clinic study published in 1999, identified fungi as a leading cause of many respiratory problems, and a contributor to nearly 100% of chronic sinus infections. In addition to allergies, the Mayo study suggests that many people also develop a different kind of immune system response to fungi.
Molds and fungi produce at least two types of potential allergens: (a) Mycelia produced enzymes, and (b) Fungal spores. Regarding the former, molds feed off decomposing plant and animal matter and grow by producing filament-like extensions called “mycelia.” These filaments secrete enzymes that can digest carbohydrates and proteins. These enzymes are very small and can go airborne in some form. In heavy concentrations, mold enzymes may become allergens. As to the latter, molds reproduce by giving off huge numbers of mold spores into the air, similar to plants releasing pollen. When airborne mold spores settle on organic matter, new mold growth starts. As protein is a significant component of mold spores, they may trigger an allergic reaction when inhaled. Such spores can be as small a 2 microns (Aspergillus fumigatus) and as large as 140 microns (Alternaria).
A particularly good environment for the growth of mold spores is found in carpet, carpet tile and upholstery. For example, fungi are deposited on the carpet through the everyday traffic of people and animals, food and beverages spilled on the carpet, and animal and infant waste. Further, airborne fungi and spores carried in from outside or carried through the heating or cooling system can accumulate on carpet and upholstery. Soil and moisture in carpet can provide nutrients for the growth of the fungi. Moreover, certain fungal spores are capable of remaining viable in a dormant state on carpet for long periods of time until they are provided adequate sustenance.
In addition to mold spores, the common house dust mite is an important cause of asthma, rhinitis, atopic dermatitis eczema in allergic individuals. For example, the mite Dermatophygoides pteronyssinus has been identified as a major source of house dust allergen. This mite and the related mites D. farinae, D. microceras and Euroglyphus maynei are the predominant house dust mites in temperate climates in North America, Australia and other areas.
Adult mites are approximately 300 microns (3/10 mm) in size, having developed over approximately 25 days through egg, larval and nymph stages. Adults live for 2 to 3½ months, during which time each female can produce about 20-40 eggs. Dust mites are photophobic, living deep in pillows, mattresses, carpets, upholstered furniture and other soft materials. Literally millions of mites can inhibit a single bed or rug.
A major dust mite allergen is present in mite faecal particles. Each mite produces about 20 faecal particles per day, and more than 100,000 of them may be present in a gram of dust. These particles vary from about 10 to 40 microns in size, comparable to the size of mold spores, and become airborne during domestic activity such as making beds and vacuuming carpets.
Although carpets and upholstered furniture are major sites of mold and dust mite growth, many allergic individuals are unable or unwilling to remove these from their home. Ordinary vacuuming does not remove mold and dust mites or significantly decrease mold and dust mite allergen levels, and in fact, vacuuming of carpets with the usual household appliances actually increases the amount of airborne dust. However, the use of special filters and/or the employment of central vacuuming systems have been helpful. Nevertheless, vacuuming alone seldom removes all of the mites or molds.
Thus, it would be desirable to have an effective method of controlling the growth of fungi such as molds in carpets and other textile substrates. It would also be desirable to have a method for controlling both fungal growth and house dust mites in carpets and other textile substrates.